1. Field of the Invention
This invention relates to a contactless system for monitoring the condition of the body or either a human or an animal and providing an alarm upon detection of a cessation of activity for a predetermined time.
2. Description of the Prior Art
The field of respiration and heart monitoring has generally been addressed in the prior art to types of devices which are used in hospitals and which have a level of sophistication requiring complex circuitry and a sizable expense. These monitoring devices have usually taken the form of respiration monitors which are used mainly in hospitals to signal a nurse when a human patient has stopped breathing. Among the most prominent of these devices is the monitoring device which utilizes the connection of electrodes directly to the skin of a patient in order to sense electrical resistance changes during respiration in the skin surrounding the expanding and contracting chest cavity. Quite obviously the connection of electrodes directly to the patient is not only a problem with regard to providing satisfactory contact due to irritation and skin rashes which result from a saline solution commonly used to provide satisfactory contact but also, this method provides several problems with regard to maintaining the contact as the patient moves.
One of the more pertinent problems in recent years has been the detection of apnea which occurs in infants and is primarily a cessation of voluntary breathing. This problem has come to be known as "the sudden infant death syndrome" (SIDS). As is now known in the medical field, the monitoring and surveillance of infants and especially infants who have been determined to be high risk during the critical first six months is seen to save many lives and at least provide information concerning the cause of this syndrome.
Quite obviously, the continuous monitoring of an infant for its first six months of its life is a process which cannot take place in a hospital because most of the problems with the detection and the determination of this syndrome is the fact that there are no warning signs which are given prior to its occurrence. Therefore, home monitoring is the most useful and most assuring method of saving lives. The basis of operation for the detection of the syndrome is the cessation of breathing which can be corrected by cutaneous stimulation. In other words, once breathing has stopped and all heart functions have stopped for a period of anywhere from 10 seconds to a minute, the infant's life may still be saved if the proper technique is used. However, most prior art devices require an extreme expense on the part of the parents to either rent or purchase the complicated devices for the home monitoring. Furthermore, these devices have problems with regard to false alarms primarily because of proper placement and retention of the sensor on the child who turns or moves in his sleep.
More recent attempts to solve these problems involve the use of pressure monitoring devices which rely on a monitoring of the activity of a child by changes in a pressure transducer located beneath the child, which changes are induced by the breathing of the child. These transducer devices such as shown in U.S. Pat. No. 4,033,332 require an active electrical bias for the pad upon which the infant is resting. In other words, these devices produce a change in the electrical capacitance in the pad when the child moves, which change is pressure related, and which change causes a signal to be developed which can be monitored. When the changes in the pressure have ceased for a period of time no change in capacitance is detected and an alarm is registered.
As indicated, these types of pressure monitoring devices require both an electrical circuit for the pad and for the monitoring of the output signal from the pad. Thus, not only must the cost of the device be extremely high but is must also be properly adjusted for the weight of the child, which changes the capacitance detected, and for the proper electrical functioning of the two separate circuits for the pad and for the signal developed from the pad.
Aside from the obvious requirement in the prior art of a separate power supply for the pad structure which requires a 110 volt source, there is the associated psychological and convenience barrier in the mind of the parents who may be apprehensive about placing something underneath their child or very close to their child which is plugged into an electrical outlet for long periods of time. Another inherent disadvantage is that these type of monitoring systems may not be used in bassinetts or portable carriers because of their size and the obvious requirement of a 110 volt source.
Lastly, the criticality of the weight factor with regard to the adjustment of the device would require adjustment of the sensing device as the weight of the child increases with age, and of course would be sensitive to other weighted objects in the crib such as toys, stuffed animals etc.
It is the object of the present invention to provide a passive contactless monitoring device which overcomes the disadvantages of the prior art.